This invention relates to a magnetic head used in a magnetic storage device, a method for making the same, and a magnetic storage device using such magnetic head. More particularly, this invention relates to a giant magnetoresistive (GMR) effect type magnetic head with a magnetic recording head of new structure.
As miniaturized magnetic storage devices with large capacity are developed, the volume per one bit recorded on a magnetic medium has rapidly become smaller. A magnetoresistive effect type head (hereinafter referred to as xe2x80x9cMR headxe2x80x9d) can detect a magnetic signal generated by this micro bit as a larger reproduced output. The MR head is described in IEEE Transactions on Magnetics MAG7 (1971)150, titled xe2x80x9cA Magnetoresistivity Readout Transducerxe2x80x9d. Further, lately, a giant magnetoresistive effect type head (hereinafter referred to as xe2x80x9cGMR effect type headxe2x80x9d) using giant magnetoresistive effect (hereinafter referred to as xe2x80x9cGMR effectxe2x80x9d) which can create significantly higher output than that in the former MR head has been put into practical use.
The GMR effect is classified into several kinds by the difference of mechanism to give a variation in magnetic reluctance. Among them, a magnetoresistive effect generally called spin-valve effect can generate a large variation of resistance by a small operating magnetic field because the variation of resistance corresponds to the cosine between the magnetization directions of two adjacent magnetic layers. Because of this advantage, the GMR effect type head using spin-valve effect has become the main stream of GMR effect type heads now being developed.
The GMR effect type head using spin-valve effect is described in IEEE Transactions on Magnetics, Vol. 30, No. 6 (1994) 3801, titled xe2x80x9cDesign, Fabrication and Testing of Spin-Valve Read Heads for High Density Recordingxe2x80x9d. In the GMR head disclosed in this literature, one of two magnetic layers which generate spin-valve effect includes an anti-ferromagnetic film laminated on that magnetic layer. As a result, its magnetization is pinned by exchange coupling field generated between the both so as to be substantially aligned into the magnetic-field direction of a medium which goes into a magneto-sensitive portion of the head, thereby forming a magnetization-pinned layer. The other magnetic layer being located adjacent to the magnetization-pinned layer through a conductive layer such as Cu forms such a magnetization-free layer that can change the direction of magnetization freely to the magnetic field of medium. Since the description below mainly relates to the GMR effect type head using spin-valve effect, the GMR effect type head using spin-valve effect will be hereinafter called xe2x80x9cGMR headxe2x80x9d.
FIG. 2 is a plan view showing the structure of a GMR head that is seen from an air bearing surface (ABS) opposite to an medium. Also, FIG. 1 is a cross sectional view, cut along the line A-B of FIG. 2, showing the inner structure of the GMR head. The GMR head has such a composite structure that a reproducing element and a writing element are combined. In the GMR reproducing element, a magnetic isolation layer 3, an insulator, is provided between a laminated layer of lower shied 2 and upper shield 6 on ceramic 1 composing a slider. In its center region 4, a spin-valve structure which generates GMR effect is allocated, while at the both ends of the center region 4, terminal regions 5 to supply electric current and bias magnetic field to the spin-valve lamination structure are formed.
Further, while using the upper shield 6 as a first magnetic pole, onto the surface (upper surface) of the first magnetic pole 6 on the opposite side of the GMR element, a second magnetic pole 11 (hereinafter referred to as xe2x80x9cupper magnetic polexe2x80x9d) is laminated in parallel to the first magnetic pole 6 through a magnetic gap 7. As shown in FIG. 1, a coil 9 sandwiched by an insulator 8 and an insulator 10 is allocated slightly behind the first magnetic pole 6 and the second magnetic pole 11. Writing and recording onto the medium are conducted by magnetic flux leaked from the magneto-gap 7 between the first magnetic pole 6 and the second magnetic pole 11 that are magnetized by the magnetic field generated by the coil 9. This inductive recording head (hereinafter called xe2x80x9cID headxe2x80x9d) and the reproducing head by GMR mentioned above form an integrated lamination. In general, practical GMR heads employ a composite structure of the ID head and the reproducing head as shown in FIG. 2.
On the other hand, conventional type MR heads using magnetic anisotropy have been also improved to get higher density, and have become able to offer a high density up to about 3 gigabit per square inch. To compete with such an improvement, the storage density of GMR heads of the next generation needs to be in a high-density region of more than 3 gigabits per square inch. Therefore, substantially desired are GMR heads that have a high density recording and reproducing of more than 3 gigabits per square. As a result, a magnetic storage device composed using such a GMR head can achieve a high density recording/reproducing device of more than 3 gigabits per square inch.
Also, as the output of reproducing head, although not limited to the GMR head, becomes higher, the ID head that offers the recording function to a magnetic medium also needs the enhancement of recording performance toward higher density. Especially, in a case that such high density recording as mentioned above is conducted, further improvement of magnetic media for a higher coercive force is required. Namely, in raising the storage density, in order to make the transition length of magnetization recorded on magnetic media smaller and also in order to hold magnetization stable even if the transition length of magnetization per bit becomes shorter, it is necessary for the magnetic media to have further high coercive force. Until now, the development to increase the recording magnetic field of ID head itself has been vigorously conducted so as to conform to a magnetic media with high coercive force suited for the high density recording.
Conventionally, as a magnetic core of ID head, a plated film of Ni-Fe with Ni content ratio of about 80% (hereinafter referred to as xe2x80x9c80 NiFexe2x80x9d) has been used. It is reported that the 80 NiFe material has a saturation magnetization (Bs) of about 1 T(Tesla) and offers the recording of 3 gigabits per square inch (IEEE Transactions on Magnetics, Vol. 32, No. 1, 1996, pp. 7-12 xe2x80x9c3 GB/in2 recording demonstration with dual element heads and thin film disksxe2x80x9d).
Also, it is suggested that in order to conduct the recording of more than 5 gigabits per square inch, instead of the 80 NiFe, for example, the adoption of a NiFe plated film with Ni content ratio of about 45% (hereinafter referred to as xe2x80x9c45 NiFexe2x80x9d) is useful (IEEE Transactions on Magnetics, Vol. 33, No. 5, 1997, pp. 2866-2871 xe2x80x9c5 GB/in2 recording demonstration with conventional AMR dual element heads and thin film disksxe2x80x9d). The 45 NiFe material has a saturation magnetization of about 1.6 T at the maximum. Further, it is reported that using the 45 NiFe material, the recording of about 12 gigabits per square inch becomes possible (xe2x80x9c12 GB/in2 recording demonstration with SV read heads and conventional narrow pole-tip writexe2x80x9d, IEEE Transactions on Magnetics, Vol. 32, No. 1, 1996, pp. 7-12). In addition to these, Japanese patent application Laid-open Nos. 8-212512 and 11-16120 disclose examples using a NiFe plated film with Bs of about 1.6 T.
Other than the NiFe plated film, there are some cases that a high Bs material formed by sputtering is used. For example, Japanese patent application Laid-open No. 10-162322 discloses the use of a Co system amorphous material represented by a CoTaZr sputtered film. The Co system amorphous film can offer a high Bs up to about 1.5 T. Further, Japanese patent application Laid-open No. 7-262519 discloses the application of high Bs material such as iron(III) nitride. The iron-nitrogen system material may offer high Bs up to about 1.9 T.
In the process of making an ID head of magnetic head, when forming a predetermined shape of magnetic pole using a magnetic material such as NiFe, the plating method is frequently used to laminate the magnetic material. Namely, using the plating method, a desired pattern can be obtained by first forming a photoresist frame with a predetermined shape of magnetic pole exposed, next growing a plated film into the frame. Therefore, this method is excellent in simplifying the fabrication process. In addition, this method is also advantageous in lowering the cost. Accordingly, in making a thin-film magnetic head using a NiFe film material that can be formed by plating, the plating has been the standard method.
On the other hand, in case of using a magnetic material to be formed by sputtering method, a desired pattern of magnet pole is obtained by forming a photo resist mask with a pattern of the magnet pole on a magnetic film that is formed in advance, then etching it by using ion beam. This method has some drawbacks below. Firstly an expensive ion beam etching apparatus needs to be used. Secondly a long processing time is required to pattern a magnet-pole film as thick as several xcexcm. Thirdly the tip of magnet pole that decides the recording width to medium is difficult to form at a narrow width.
For example, in the upper magnetic pole 11, the patterning is applied to part where a large difference of level is formed with the coils 9 and the upper and lower insulating layers. But, it is technically very difficult to conduct the processing to obtain a good shape in such part as has a large difference of level. To avoid such difficulty, Japanese patent application Laid-open No. 7-262519 discloses a method that only the tip portion of magnetic pole is first formed prior to forming the large uneven part with the coils and the insulating layers, and then forming an iron-nitrogen film on the part by sputtering. However, the forming of the tip portion of magnetic pole itself needs to use ion beam etching, and therefore the above method does not give a low-cost manufacturing in view of manufacturing equipment. As explained above, when a sputtered film is applied to a magnetic pole, the complicated process is needed to obtain a predetermined magnetic film pattern, and also it becomes a factor of rising the cost.
Researches have been conducted on such a material system that the plating method can be, like conventional NiFe, applied to in laminating the magnetic material and a high Bs more than 1.6 T being obtained in 45Ni-Fe can be obtained. As one of them, a Co-Fe-Ni system material is deemed to be a hopeful material system that can achieve high Bs more than 1.6 T in the form of a plated film. As mentioned below, for example, the Co-Fe-Ni system material itself actually can achieve high Bs, and means for making its plated film is also proposed.
Japanese patent publication No. 63-53277, FIG. 1, shows a line of non-magnetostriction in a ternary composition of Co-Fe-Ni, specifically, a line of magnetostriction xcex s=0 in a Co-Fe-Ni plated film, which is cited from Journal of Applied Physics, Vol. 38, 1967, pp 3409-3401. Also, FIG. 2 of the same patent publication shows a plot of intrinsic magnetic flux density in ternary composition of Co-Fe-Ni, and from this FIG. 2, Bs in Co-Fe-Ni plated film can be immediately calculated. These two figures proves that the magnetostriction xcex s becomes substantially zero in around Co80%-Fe10%-Ni10% and Bs becomes about 1.6 T. Japanese patent publication No. 63-53277 also suggests an example of composite of electroplating bath and plating conditions to be used when conducting Co-Fe-Ni plating of above composition.
Japanese patent application Laid-open No. 6-346202 describes about an improving means to attempt compatibility of low magnetostriction and high Bs around Co80%-Fe10%-Ni10% formerly proposed in Japanese patent publication No. 63-53277, namely, the adjustment of crystallinity of Co-Fe-Ni is conducted. As the result of adjusting the crystallinity, a Co-Fe-Ni plated film with Bs of about 1.7 T is obtained at magnetostriction xcex s less than 5xc3x9710xe2x88x926. Also, Japanese patent application Laid-open No. 7-3489 describes that in around Co80%-Fe10%Ni10%, a plated film with low coercive force and Bs in the range of 1.3 T to 2 T was obtained by adjusting the crystallinity. Meanwhile, the details of a concrete composition having Bs as high as 2 T are not disclosed.
Japanese patent No. 2821456 describes about a high-purity plated film, which has a sulfur content ratio reduced to 0.1% or less, obtained by forming a Co-Ni-Fe plated film using a plating bath composite not including an additive such as saccharin. In this high-purity plated film, compared with the plated film made by the method in Japanese patent publication No. 63-53277, a composition of mixed crystal composed of crystal system fcc and bcc moves to a region including more Fe content, and magnetostriction is decreased to a practically usable level by the composition. In addition, it is disclosed that a Co-Ni-Fe plated film obtained offers Bs as high as 1.9 T to 2.2 T as well as a soft magnetic characteristic with magnetizing ratio of 2.5 Oe or less.
As mentioned above, in the Co-Ni-Fe system plated film, a composition to achieve a practical soft magnetic characteristic required to a magnetic material for magnetic head greatly varies by the crystallinity or the content of material mixed into the plated film. In this regard, as disclosed in Japanese patent No. 2821456 etc., it is proved that the Co-Ni-Fe system material is capable of achieving a very large Bs and an excellent soft magnetic characteristic by adjusting the crystallinity and the content of material mixed into the plated film.
In forming a plated film using the plating method, a conductive film, a seed layer is first formed on a substrate by physical vapor deposition method such as sputtering and vapor deposition, and then electric current is supplied to the seed layer in a plating bath to form a required film. Conventionally, in the case of NiFe system plated film, NiFe film is also used as the seed layer.
On the other hand, even when a magnetic material with Bs of 1 T or more is used for the upper magnetic pole, if the seed layer composed of a magnetic material with Bs of 1 T or less is allocated as its base layer, there occurs a problem that, in comparison with the case that Bs of the base layer is also 1 T or more, the rise of recording magnetic field becomes later and the recording magnetic field itself becomes weaker. Therefore, in order to make the most of advantage of the high Bs upper magnetic pole itself, it is also necessary for the seed layer laid thereunder to use a magnetic material with high Bs of 1 T or more. As a material with such large Bs suitable for the seed layer, there is a CoNiFe film or a CoNiFeX film (X is at least one element selected from Cr, Ti, V, Ru, Rh, Pd, Os, Ir and Pt) having a saturation magnetic flux density of 1.6 T to 2 T and being formed by physical vapor deposition method.
The inventors of this invention have discovered that forming the CoNiFe film or CoNiFeX film to be used as the seed layer by physical vapor deposition method, and then forming, thereon, a Co-Ni-Fe plated film of desired composition, for example, a Co-Ni-Fe plated film with Bs that is selected from the range of 1.9 T to 2.2 T by plating method offer that the seed layer itself provided as the base layer also has a large Bs of 1.6 T to 2 T, thereby the advantage of large Bs of the plated film used as the upper magnetic pole can be obtained sufficiently.
However, in forming actually the Co-Ni-Fe plated film using the CoNiFe film or CoNiFeX film, the seed layer formed by physical vapor deposition method, there occur some problems mentioned below.
First, when forming the plated film with a composition of about 80%-Fe10%-Ni10%, the CoNiFe film or CoNiFeX film, the seed layer formed by physical vapor deposition method melts into a plating bath. This causes a variation in composition of the plating bath near the seed layer, so that a plated film with high Bs intended can not be formed. In the extreme case, the seed layer at the window portion of frame-resist is partly lost, therefore preventing the plated film from being formed.
Next, there is also a case that during the plating, part of the seed layer melts into the plating bath, thereby a gap is created between the seed layer and frame-resist. On that occasion, the plating bath soaks into under the frame-resist, which causes an abnormal shape of the plated film. Namely, the upper magnetic pole becomes a different shape from desired one.
In both of the above cases, the Co-Ni-Fe plated film obtained does not show a desired characteristic, and becomes a factor to lower the reliability and the productivity of ID head that is required to have a high density recording performance.
Accordingly, desired is a method of forming Co-Ni-Fe plated film that prevents the CoNiFe film or CoNiFeX film, the seed layer formed by physical vapor deposition method from melting into the plating bath, thereby giving a Co-Ni-Fe plated film with desired composition and shape.
Accordingly, it is an object of the invention to provide a magnetic head suitable for high density recording which adopts an upper magnetic pole of new structure where the disadvantages caused by using a CoNiFe film or a CoNiFeX film formed by physical vapor deposition method as a seed layer are solved and ID head used for recording onto a magnetic medium itself shows high reliability and production efficiency.
It is a further object of the invention to provide a method for making a magnetic head by which the above structure of upper magnetic pole can be made up high reproduction ratio, and also to provide a magnetic recording device using the magnetic head suitable for high density recording.
It is a still further object of the invention to provide a structure of an upper magnetic pole (magnetic core for recording) suitable for ID head which can attain higher output of reproducing heads not restricted to GMR head together with higher density recording performance, and to provide a magnetic head adopting such structure of upper magnetic pole.
The inventors of the invention found out the following facts.
For example, in a magnetic head with structure shown in FIG. 4, an upper magnetic pole (second magnetic core) composing ID head used in magnetic recording is formed to be a laminated layer type magnetic core comprising a first magnetic layer located at the most neighboring position to an electrical insulating layer forming magneto-gap (recording gap) which is provided between a lower magnetic pole (first magnetic core) and the upper one, a second magnetic layer laminated thereon, and further a third magnetic layer which is formed into a desired shape on the second magnetic layer using a frame resist. In this structure, when the second magnetic layer is composed of a magnetic material which substantially does not melt into a plating bath for the third magnetic layer, the first and second magnetic layer do not melt into the plating bath, and therefore occurrence of abnormally shaped plated film due to invasion of the plating bath into the under portion of the frame resist can be prevented. In addition, when the structure of the laminated layer type magnetic core is adopted, the density of magnetic flux leaked from between the magnetio-gap depends mainly on the saturation magnetic flux density Bs of the first magnetic layer, and also when a magnetic material with large saturation flux density Bs is used in the third magnetic layer, density of the magnetic flux becomes higher corresponding to Bs of the first magnetic layer and Bs of the third magnetic layer. Even if the saturation flux density Bs of the second magnetic layer itself is smaller than Bs of the first magnetic layer and Bs of the third magnetic layer, the magnetic flux density leaked from between the magneto-gap becomes higher corresponding to Bs of the first magnetic layer and Bs of the third magnetic layer. This invention is made on the basis of such knowledge.
According to the first aspect of the invention, a magnetic head with an inductive head type recording head used in recording onto a magnetic medium, comprises:
an inductive head type recording head of such structure as being provided with a magneto-gap layer of non-magnetic and non-conductive material between a first magnetic core and a second magnetic core, and an exciting coil electrically isolated from the first magnetic core and the second magnetic core, wherein a part of magnetic flux from magnetic cores excited by the exciting coil leaking from the magneto-gap layer, and recording onto the magnetic medium being conducted by the leaking flux;
wherein the second core is a laminated type magnetic core comprising laminated three kinds of layers of a first magnetic layer allocated most adjacently to the magneto-gap layer, a second magnetic layer laminated on the first magnetic layer, and a third magnetic layer formed to be a desired shape on the second magnetic layer by frame plating, and as the second magnetic layer, a magnetic material which substantially does not melt while plating of the third magnetic layer is conducted is selected.
In the magnetic head, it is more favorable that the third magnetic layer comprises at least one layer of layers composed of CoNiFe system magnetic material. The third magnetic layer composed of CoNiFe system magnetic material may be such structure that it comprises, in addition to a layer of CoNiFe system magnetic material, a layer of NiFe system magnetic layer laminated with the CoNiFe system magnetic material, and at least one layer of the layers of CoNiFe system magnetic material is allocated so as to contact with the second magnetic layer.
In addition, it is more favorable that the first magnetic layer is composed of a CoNiFe system magnetic material, or a layer of a magnetic material whose main constituent is CoNiFeX, where X is at least one element selected from a group of Cr, Ti, V, Ru, Rh, Pd, Os, Ir and Pt.
Furthermore, in the magnetic head according to the first aspect of the invention, a layer of a non-magnetic material may be provided as a base layer for the first magnetic layer. Favorably, the base layer includes at least one layer of a film of non-magnetic material selected from a group of Ti, Ta, Cr, TiW, TaN, TiN, Mo, Si and SiN. Also, thickness of the base layer may be selected from a scope of 10 nm to 50 nm.
On the other hand, in the magnetic head according to the first aspect of the invention, for example, in case that the third magnetic layer includes a CoNiFe system magnetic material, it is favorable that a layer of a magnetic material of NiFe system alloy is used in the second magnetic layer. Also, it is more favorable that thickness of said second magnetic layer is selected from a scope of 5 nm to 100 nm.
A magnetic head according to the invention may comprise, in addition to the inductive head type recording head, a magnetoresistive effect type read head used when reading record on a magnetic medium. The magnetoresistive effect type read head may be a structure that it comprises a first magnetic shield and a second magnetic shield opposing to each other and an insulating layer isolating between them, and one of the opposing magnetic shields is formed, together with the first magnetic core of the inductive type recording head, into one body. Also, one of the opposing magnetic shields may be used as the first magnetic core of the inductive head type recording head.
According to the second aspect of the invention, a magnetic recording-reproducing device comprises the magnetic head according to the invention installed therein.
According to the third aspect of the invention, a method for making a magnetic head, comprises:
in making the second magnetic core composing said inductive head type recording head, a process for making a first magnetic layer composing the second magnetic core, a second magnetic layer formed on the first magnetic layer, and a third magnetic layer formed to be a desired shape on the second magnetic layer by frame plating comprises the steps of:
forming the first magnetic layer using physical vapor deposition method;
forming the second magnetic layer using physical vapor deposition method;
forming a desired shape of resist frame on the second magnetic layer; and
forming, using the desired shape of resist frame, the third magnetic layer formed by frame plating by electroplating method by supplying electric current at least to the second magnetic layer.